Plastic handles of various shapes and sizes are found on many household items. Such household items include toothbrushes, shaving razors, hairbrushes, pens, tools, kitchen appliances and kitchen utensils. These household items have a variety of functions, but in most cases, it is desirable for the user to grip the handle of these items firmly, so that it does not fall out of the user's hand. In other cases, such as with a knife or fork or a tool, it is desirable for the item to be gripped with even more firmness so that it can be leveraged.
Because the handles of these household items are normally made of a hard plastic, the simplest tasks can become problematic. As in the case of a toothbrush or shaving razor, the handle generally come into contact with water. When the toothbrush or razor is wet, it is difficult to grip and may slip out of the user's hands. Other items such as tools or kitchen utensils can have handles that are difficult to hold onto or uncomfortable to grip because of the hardness of the plastic material. For persons suffering from arthritis, carpal tunnel syndrome or other hand injuries or infirmities, using these basic household objects can become more difficult or even impossible.
Most people would prefer to grip objects with a softer handle that is more soothing to the touch and easier to grip. Accordingly, a need exists for a soft grip handle that can be grasped firmly and comfortably and which requires minimum strength and dexterity to grip and maneuver.
U.S. Pat. No. 4,250,273 suggests a thermoplastic elastomer composition comprising from about 10 to about 50 parts of a crystalline olefin polymer, from about 80 to about 15 parts by weight of a random styrene-butadiene rubber, and about 5 to about 55 parts by weight of a highly saturated elastomer.
U.S. Pat. No. 4,340,684 suggests a thermoplastic elastomer composition comprising from about 10 to about 50 parts of a crystalline olefin polymer, from about 80 to about 15 parts by weight of a random styrene-butadiene rubber, and about 5 to about 55 parts by weight of a highly saturated elastomer, where in the blend was partially cured so that a thermoplastic elastomer was formed which had a melt flow index of at least 1.0 when tested in accordance with ASTM D 1238 condition L at a load of 100 pounds. The authors suggest that when the melt flow rate of the formed blend was less than 1.0, thermosetting formulations were formed.
U.S. Pat. No. 4,343,918 claims the process for making a thermoplastic elastomer composition comprising from about 10 to about 50 parts of a crystalline olefin polymer, from about 80 to about 15 parts by weight of a random styrene-butadiene rubber, and about 5 to about 55 parts by weight of a highly saturated elastomer.
U.S. Pat. No. 4,927,882 claims a thermoplastic elastomer composition having a compression set less than about 30% and produced by dynamic vulcanization of SBR to form a dispersed phase of crosslinked SBR in a co-continuous matrix of SEBS and polypropylene. The compositions had specific use in the pharmaceutical applications.
There is a growing demand for a wide variety of articles that are soft and soothing to touch. It is, of course, also important for these articles to have the strength, durability, and rigidity needed in the applications where the articles is used. This can be accomplished by overmolding a soft thermoplastic composition onto on a hard thermoplastic substrate. However, there is a need for a soft thermoplastic elastomer composition that can be overmolded onto a hard thermoplastic resin substrate wherein the soft thermoplastic composition has lower hardness, good oil resistance and low compression set. There is currently a need for a thermoplastic composition that has superior feel and comfort as characterized by a lower modulus to that which is obtained by using syndiotactic polypropylene copolymer.